Comparison of light effects on periphytic algal biomass and relative species abundances in open and shaded areas of a lotic waters.

Abstract

The purpose of this study was to analyze the effects of light on algal biomass and relative algal cell type abundances in open sunlight and shaded areas. Algal biomass and chlorophyll a measurements were used to compare the production of algae cells in these areas. Ash-free dry weight (AFDW) was used to determine biomass. This experiment took place in Maple River of Pellston, Michigan (Lat. 45 30.5' N, Long. 84 46' W, SE 1/4 of Sec. 14 T36N R4W). The study began on July 28, 1993 and was completed on August 4, 1993. Algal biomass, chlorophyll a content and relative abundances were expected to differ substantially, although, the relative abundances of algal cell types did not very significantly (T calc = 17.5, T crit = 10, alpha = 0.05). Surprisingly, the average light intensities did not vary enough, statistically, under the shaded and in the open areas chosen, (T calc = 10, T crit = 10). This statistical analysis could be due to error in the procedure. Considering these factors, it was determined that light intensities did increase algal biomass, but did not have an effect on relative species abundances due to the biology of several algae genus.